Classic Rally Andorra

A band with two faces

There are few companies that have influenced the car tire as profoundly as Michelin. Founded in 1889 by brothers Édouard and André Michelin in Clermont-Ferrand, the company is responsible for some of the most revolutionary breakthroughs in tire history: the removable pneumatic tire in 1891, the first radial tire in 1946, and — less well-known but just as important — the world's first asymmetrical tire in 1965.

That latest innovation is called the Michelin XAS. And anyone who buys a sports car today with a Pilot Sport, Pirelli P Zero, or Bridgestone Potenza is driving on a principle that was first conceived in a French laboratory sixty years ago.

The problem that the XAS had to solve

In the mid-1960s, sports cars became faster, corners sharper, and highway speed limits higher. A conventional symmetrical tire—which looks identical on both sides and can be mounted in any direction—could no longer keep up. It was a compromise: reasonably good at everything, excellent at nothing.

The fundamental problem is that the inside and outside of a tire are exposed to completely different conditions while driving. The inside of the tire must drain water. The outside must provide grip in corners and stability on dry roads. But if the tread is identical on both sides, it can only perform one task optimally at a time. The rest is a compromise.

Michelin drew the logical conclusion: if the conditions on both sides of the tire are different, the treads must be too.

The solution — one band, two tasks

The Michelin XAS introduced a tread with a clear inside and outside — the name on the sidewall indicates how the tire should be mounted, an absolute first in tire technology.

The outer side of the tire features smaller, stiffer tread blocks that create more contact surface with the road. Result: more grip in corners on dry roads and less road noise on the highway. The inner side has larger cavities and deeper grooves that quickly drain water away from the contact patch. Result: better aquaplaning resistance on wet roads.

Two halves. Two tasks. One band. It sounds simple — but no one had thought of it before.

The cars that made the XAS big

A revolutionary tire needs revolutionary cars to prove its worth. The Michelin XAS got them. In the 1960s, the Porsche 911, 912, and 914 came standard with the XAS — a choice Porsche made deliberately because no other tire could handle the driving dynamics of the rear-engine 911 so well. The Citroën DS — the car that made it cool to be unconventional — also relied on the XAS.

Lancia, Austin-Healey, Lotus, Aston Martin, Peugeot, Alfa Romeo, and Renault followed. The XAS received a V-speed index, capable of top speeds of up to 240 km/h — an impressive achievement for a production tire category in 1965.

Citroën, among others, embraced the Michelin XAS tire with the DS early on.

The inheritance

The XAS itself has long been out of production. But its principle is everywhere. Virtually every modern performance tire — from the Michelin Pilot Sport Cup 2 to the Pirelli Trofeo R — uses the asymmetrical tread pattern that Michelin first applied in 1965.

What began as a solution for the Porsche 911 driver who took corners too sharply has grown into the standard for every sports tire on the market. Six decades later, in a tire segment that is more competitive than ever, the XAS principle is still the foundation upon which every manufacturer builds.

The Michelin XAS didn't just change the tire — it changed how engineers think about grip, water, and the road. That is the definition of revolutionary.